Ammoniated acid activated montmorillonite catalyst and preparation thereof



Sept. 21, 1948. v w w. w.`GARY ET AL M/fe ArroQNeY.

""gases useful as catalysts.

Patented Sept. 21, 1948 AMlVIONIATED ACID ACTIVATED MONTMO- RILLONITE CATALYST AND PREPARA TION THEREOF Wright W. Gary, Los Angeles, and Robert B. Secor, South Gate, Calif., assignors to Filtrol CorporatiolnLos Angeles, Calif., a corporation of Delaware Original application February 7, 1944, Serial No.

521,446, now Patent No. 2,432,746', dated December 16, 1947. Divided and this application July 3, 1947, Serial No..758,776

15 claims.- (ol. 252-196) `This process relates to a method of producing active catalytic material of the bentonite clay type. As is well known, bentonitic clays, particularly montmorillonite y clays, Classifiable as sub-bentonites, may, on acid treatment, be con-- verted into active adsorbents for' liquids and VSuch catalysts have found a Wide application in catalytic cracking of petroleum.

vThe clay is essentially an alumino silicate, in which part of the alumina is substituted by MgO and inwhich the hydrogen of the montmorillonite acid is replaced by base exchange with Ca'and Mg and other ions. Such clays may also contain iron in'the'form of silicates or in the form of other compounds such as sulfides or as lattice iron. A typicalanalysis of such clays (Cheto clay) is given by the following;

Per cent Silica (Si02) 67.3

` Alumina (A1203) 19.5 Iron oxide (Fe203) 1.8 Magnesium oxide (MgO)y 6.9

Calcium oxide (CaO') 3.2 Manganese oxide (MnO) 9.8 Titanium oxide (TiOz) 0.3

The natural clay is fundamentally montmorillonite, having base exchange capacity of about 124 millicquivalents per 100 grams volatile free substance, this capacity being saturated largely with alkaline earth ions such as' calcium and magnesium. Natural claytherefore can be de- 1 iined ras a calcium or magnesium montmorillonite.

Upon acid treating the clay, one of the rst reactions is the replacement of the calcium and magnesium ions to form a product which is predominately hydrogen montmorillonite. Thismaterial may be termed a clay acid inthat it shows I acidic properties. n relatively light acid treatment calcium land magnesium are not completely removed. As the acid leaching continues alumina andv also iron oxide present as impurities are re- 'moved Hydrogen enters into the lattice of the leached clay as the alumina is extracted and there is a loss in base exchange capacity.- It is believed, however, that as long as the resultingv product isnot subjected to rigorous treatment,

l such as extensive dehydration, the hydrated silicaQwhich is part of the original montmorillonite lattice and which is left as a result ofthe leaching, is isomorphic with the original mont- 2 morillonite; that is to say, the silica and oxygen skeleton of the original montmorillonite is `retained. As this extraction continues Withreduotion of base exchange capacity, as explained, the calcium and magnesium and alumina are more f and more completely removed, and a material of lowered base exchange capa-city is left.

The degree of removal of R203, namely A1203 and Fe203, is a function of the degree of extraction, that is, it depends on the time, temperature, and concentration of acid employed. The result of this increasing degree of extraction is not merely a difference in degree of improvement in adsorptive and catalytic efliciency, since these properties do not proceed in step with the Adegree of extraction. Thus, the first of 3% or 4% '7 of A1203 removed gives the largest amplification of adsorptive and Icatalytic efficiency, and on a further extraction these efficiencies increase further andpass through a maximum, and when the extraction is continued to reduce the R203 content to below about 10% or 12%, the efficiency falls voff and becomes as inert as the original clay when the R203 content is reduced to about 1% to 2% or 3%.

1n the acid treatment of the clay, the clay, after coarse grinding, is treated with sulfuric acid of concentration from 5% to 60%, employing a dosage of from 20 to 150 pounds of anhydrous acid per 100 pounds of clay (volatile free, i. e., no V. MJ.' The time and temperature of extraction is that necessary to give the desired degree of A1203 extraction. The degree of extraction will vary t0 yield clays yof from l0 to 20% R203.

A typical example of this procedure employes an acid strength of about 12% to 15% and an amount of acid equal to about 30 to 50 pounds of Y acidl per pound of volatile free clay. The temperature -employed is about 180 F. `to 210 The time may be about 6 to 9 hours. In the case of the clays Whose typical analysis Ais given above, the extraction is continued to 4vgive a clay with an R203 content of about 16% t0 about 17%. The time usually is about 6 hours.

` The clay is washed in Dorr thickeners and the treatment. The main bulk of `the solution .is separatedffby-decantation and washing. These salts and acid are-'thus washed out and the'clay. separated. Depending on the degree of washing,

the resultant clay will contain in adsorbed staten more or less of these salts and more or less of this acid. The retained sulfuric acid 'andWt-hefacid salts, such as alumina sulfate,v willcgive an acid reaction. The montmorillonite acid is also `a relatively strong acid. This ,residual acidity; herein called titratable=acidity, maybe determined by the methods hereinafter'set out.

`We have now discovered that a clay which has been washed to -a degree toleave aA residual titratable acidity may be furtheractivated to increase its catalytic activity by ammoniation of the. clay. The acid treated clay, which has been washedntO leave a residual -titratable acidity, is treated with ammonium hydroxide.

While We do not Wish to be bound by any theory 'i-.ofthe action of theammonia, .we believe thatfthe ::ammoni-a-reacts both with the free sulfuric-acid @and with `the aluminum'sulfateaandother'sul- `frates'wh'ich are present, adsorbed andlotherwise containedin the clay, to formammoniuml sulfate @rand hydrated alumina-andso-me otherl bases, and

also thatL-the ammonia isfadsorbed by' ythe clay t-.enitering betweenfthe :plates of the montmorillo- .:nitepcrystal structure. Additionally, Ithe ammo- ;niafenters==into ttheqclay-structure byfbase eX-,: archange vwithuthe hydrogen of the montmorillonite andfthu-s forms an ammoniumclay. t Thus, a, clay untreated Withfammonia 'may have', forexample, a vhasefexchange capacity of 40 to :110 milliequivarlentsjo which, for'ins-tance, 5 to 80 or more may.;

be-satisfied .byfbase exchangeable ammonia, the @remaining/*being satised-in `part'by Ca and in part by-Mg.

.'This; clay when subjected to--temperaturesin the rlrange of 900 to'l200o F; losessubstantially-all oi;-

-f itsam-monia. .-Anyresidual ammonium sulfate is vcdecomposed and the base vexchange .ammonia is r-removed, we believe-to -yi-eld a hydrogen .-clay.

This ammonia .compiere yis unstable at. high teniper-atures. .'yposed'at a temperature -ofaboutv5001 to 600 F. and substantially all .of the.ammonia,contained "both;` as 'ammonium sulfate and.y base. exchange .l sanunoniapis'removed by heating the lclay .to..900 to 1200`o F. This procedure `differs :also .from the tztreatment-of: the clayby-mixing theacidtreated clay with aluminum sulfate or .other soluble alu- .;:minum-.saltwand l'neutralizing the solutionwith .i2-ammonia toprecipitate the hydrated aluminafin the presence Iof the clay. No extraneous alumi- .zf numz sulfate is employed in our .process The acid activatedfclay may also be treated to .neutralizeior y'par-tiajlly neutralize the. residual :acidity: as Vherein-described by treating.. lthe .clay

"fr:containingeresidual' acidity with. other...bases Vor* metal salts-such as NaOH, .KOH in. the- Ypla-ce of f, ythe ammonia, inaccordanceW-ith Ithe procedures wherein described. The .resul-tant clay... contains sodi-um or.4 potassium sulfate or sulfates. ofthe metal employed in ythe neutralizingag-ent,. andthe acid clay is converted. intoalkaliors othermetal -clayfasg for-.instanca a-.sodium .clayton a.potas 'f'sium clay or a` calcium or .magnesium clay. The Nhydrogen offthe montmorillonite. is replaced by the alkali metal, alkaline earth me'talforother` y:metal ionwhose compoundis used as a neutralizi-.ing agent. .Suchl a clay whensubjected `tothe above @temperatures does-not .lose its base .exwchanged metal ion andthesodium.orfzpotassium for other-:sulfate stable at. thefternperatures ofv they The ammonium sulfate Ais -decom-1 drying or calcination or at the start temperal Aturezemployed is not removed-bydecomposition as lin the case of the ammonia activated clay.

In catalytic reactions such as in hydrocarbon 5 1^conversion wherein the clay in its catalytic reactions is subjected to tempera-tures up to 900 or 1000"' F. V`Vvand inf the regeneration operations wherein thespent catalyst from the catalysis is regenerated at'temperatures of 1000 to 1150 F. l0.theammoniatedclays are subjected -to tempera- -turesat-which'the' clay loses the ammonia. Thu-s, v:'...i-,lfreelay isrstfproduced as an ammonia clay and is de-ammoniated in ithe course of its use and `throughout the. major portion of its useful life it 15..is in ade-ammoniated condition. In contra- .-ldistinction,..thelalkali clays are stable and the i .base exchangeable alkali ions, which are not as useful as the base exchangeable acid hydrogen in ecatalysis employing acid activated clay are retained on the clay.

.Thissinven'tion' will bev further describediby' refverence-fto 4the accompanying drawing which illustrates-.embodimen'ts :of ouri .invention byf a .f rschematic-flow sheet.

The .mined clay=whichhas Ybeerrgroundf'to vfroman 8 to.12 Imesh is-.contained in bin Iii-rom v--whichfit is fed by alsuitable conveyor system, 'cschematically yindicatediby line.2. '.It-is` fed into 'the -acid treating chamber 3 into which hasbeen 30. charged .the acid Water through-line 5 passing via :rjline 4. AdditionalfacidY is passedv from :container B-and line 1 :into'treater 3 tolsupply'the desired quantity offacid for treatment at the desired concenltration. Steamsand air are introduced tofagi- 354 tator @and the temperature of the reaction .Vessel .is wmaintained -in this way vat 1 the 'desired level. The 'acid treated clay is discharged lthrough line 9 into lcl'lam-berfIIl iromV which the slurrypfof .clay and residual acid is pumped by pump II in line 40 'I2 into the decantaltion washing system. This is schematically shown asthreeDorr type' thickeners, although a larger number may beemployedito .l obtain' the desired treatment.

' The" slurry enters the' rstthickener 'I.3. Where -fit is mixed with'the overflowy from thickener'l 1.50 linez'I-Exandtpump"Iii-throughline lI 'I Where it enfiters intcrthckener` I8commingled with' the overfflowlfrom thickener '24 passing through llne`fI9. 'The underflow-passing'through line- 20 is pumped --by .pump .'2I through line 22 Wherev itis mixed .55.with freshwater enteringthrough 23 =and issir- -..troduced-finto thickenerl 24. f The `under-how from thickener 24 passes through line 25 and is pumped fbyepump: -26into-the'filteruZ'I. The degree of wash'ingrin the Dorrlt-hickeners and on thef-lter .issufficient tofrernove soluble salts and freesul- .-:Euric acid. f The-'residualfacidity -ofy the; clay-conf-sisting .of'adsorbed. aluminum sulfatafandfree sulfuric -aoidV willwvary'in Iequivalency from Jabout l-tofllOandV higher (milligrams of KOH yper-.gram 65.of\;dry clay, depending .on'the degree ofv washing. On its-way). to the iilterthe `clayslurryis vtreated with .sucient ammonium. hydroxide introduced through .25a` toreduce the clayfslurryv to a=pII of .lito 9,;-preferab1y 5-to 7. The filtrate iswith- -drawn through` 28. The. yiiltercake may, then @be washed with water.

,.'llheiacidtreated cakeis passed through a pug r-millA 3 IV yWhere it. ,meets the. over-sized4 material ...-passing. through line .30,as will he describedlater, and theommingledvmaterial passesthrough line `32'irito the lflash drier 33 wherein it is mixed with vhot gases generated in the flash drier. The ma- 'te'ria'l's'usually dried to' a V. M. of from l15 to 25%. The stream of gas and clay is vthen passed through line 34 into a mill 35, such as a cage mill, and the gases and clay enter the separator type in which a rotary fan sets 'up a centrifugal motion of the clayparticles, causing the separa- {tion of the desired material into two fractions, a `coarser fraction, which is removed via 39 to be passed to the pug mill 3|, and a finer fraction which is removed via line `4l). This material is elevated by elevator 4| and passed throughline l2 into a second whizzer type separator 43. .The

' coarser fraction through line '44 is treated as is described below. The finer material passes through line 45 and may be split, part or all passing through 46 for uses to be further described.

i vPart or all may be passed through line 41, as

will be later described. The gas stream separated in 48 is passed by blower 49 into cyclones 5l through line 50. `The solids separated in these cyclones are passed through line 52. The gases issuing through line 53 pass to an electrical precipitator 54 and the gases, substantially free of solids, are discharged through 55. The electrical precipitated material may be passed through line 56 to join the material in line 52 or, in part or'whole, may be discharged through line 58 for other uses. e v

AIn this extruder system the material which is kseparated through 52 isintroduced into pug mill Sil.y If desired a portion of the material separated in 56, together with some material separated from 41 and some material removed via 44 and passing through 19, may be commingled in the pug mill 60 with the desired amount of water. The amount vof water employed is that required for proper extrusion into pellets and 4usually ranges from 40 to 50%. The materialr passes from the pug mill into a screw type extruder in which the clay passes throughlarge `:orifices under extrusion pressure of an auger '-lscrew, and the extruded material is `cut into convenient lengths. It then passes into final extruder 64.' The clay pellets are re--pulped and forced through finer orices of desired idimensions, and cut into desired sized pellets. They then pass through drier 65 to storage.

" AThe pellet may range from le to 35 in diameter 4upto larger rsized pellets, depending on their use, and usually are cut off to a length l equal to their diameter.

','Instead of treating the material prior to ltration and drying, the material may be dried, separated, and the material in the pug mill 60 may be ammoniated by supplying the ammonia to the water used for making the extrudible mix. In such case the ammonia is added to the water in amounts and concentration to give the desired pH furthe clay, for example, 4 to 9 pH, preferably about 5 to 7 pH.

Instead of employing the pug mill for the ainmoniation, the dried and separated material may be suspended in an ammonia solution and agitated and the mixture filtered, dried, ground, and then extruded in the above manner.

In this speciflcatiom When we employ the terms V. M., titratable acidity, pI-I, catalytic activity for cracking, density, the values 6 thereof may be determined by the following procedures; V. .'-Five grams of the catalyst Aare Pel'elltf volait/116 matt BI 'crematie am'dz'tyr-'rhis acidity is cetermined by the so-called boil-out test, in which grams of the clay are boiled with 50 cubic centimeters of distilled water, filtered, and the filter cake washed with 50 cubic centimeters of hot distilled water. The acidity is determined by titration, using phenolphthalein indicator. The acidity expressed in milligrams of KOH per gram of sample is termed titratable acidity. Titratable acidity, unless otherwise specified, is shown as based on 20 V. M. clay.

pH.--The clay is dispersed in water in an amount greater than about 20% solids at ordinary room temperature and the pH determined by a pH meter.

Catalytic activity.-The dried catalyst pellet, such ias the pellet formed as described above, is introduced into an oven maintained at 1050 F. and the pellet maintained at this temperature for a period of i'lve hours. The catalyst is then cooled without access to air in a desccator or similar container, and upon cooling is transferred to air-tight containers. 200 cc. of the catalyst (i. e., suicient catalyst pellets to occupy 200 cc.) are then transferred into the cracking chamber of the catalyst cracking unit. The catalyst is raised to 800 F. and a Vaporized gas-oil (for example, 35.5-375 A. P. I. East Texas gasoil having 70D-'130 end-point) is passed through theunit at a rate of 30 liters of `liquid oil per hour per 20 liters of catalyst. The exiting vapors from the cracking chamber arecondensed at a temperature of F. The condensate thus collected is termed the first-cycle condensate. The gases are collected.

At the end of 10- minutes the cracking is discontinuedv and the catalyst is regenerated by raising'its temperature to 900 F. and passing air through the catalyst to convert the deposited carbon into CO and CO2. The passage of air is continued until no substantial amounts of carbon monoxide or carbon dioxide are present in the exiting gases. The exiting gases are then vpassed, to a combustion chamber and any CO ris converted to CO2. The total CO2 is determined and the carbon equivalent thereto is determined.

The air flow is then discontinued and the temperature of the catalyst isreduced to 800 F. and a second cycle of l0 minutes is carriedout in the manner previously described. Repeated cycles of regeneration and cracking are carried out. The .average of several cycles, excluding the first cycle,` is taken and is hereinafter reported in the examples given below. The gasoline is reported as volume per cent of feed, gas as weight per cent of feed, and carbon or coke as weight per centv of feed. y

The following examples of the operation of my e processare given for the purposes of illustrating,

and not for the purposes of limiting, our invention:

Example 1 kThe Cheto clay whose .analysis is givenv above was treated with 30- pounds of acid at a concentration of 12.5% for 6 hours at a temperature 2:7 of 200 to210 F. :The clayWas'washe d.to-.ia titratable acidity of 25mg. of KOI-I per. gramoi clay. `The clay was dried,-separated, andfpelleted by thelabove procedure. f-Noammoniawas used.

lThe pellets leaving ythe extruder (termed .green pellets) had a V. M. of 45.3andmwere-Ydried to a V. M. of 23.3%, and had an apparent density of.766. The clay had the following analysis:

"Per cent S102 71.5 -R203 18.40 F6203 1.7 CaO 3.1 `MgO .4.3 S03 4.7

'lIts catalytic activityr'in the above process of -cra'cking was: 410 end-point gasoline, 34.6%; "gas; 4.1%; carbon, 3.2%.

Example 2 The same clay was treated and pelleted 'in the ..same'fmanner'except that ammonia was added i to. vthe pelleting water to bring the clay -to.5-pH.

The pellet thus formed when dried to=substan l'tial-ly vthe.same`V.I-1\/I. had a densityr of .678. *Whenfused 'in the' above-process.of-fcatalysis :it "gave fthefollowing results: 410zend-point: gas- -"'oline,` 39.3% gas, 5.1% carbon, 4.4%.

Examplev 3 FAv Purvis clay,.a clay of the type previouslydefscribed, `was extracted employing pounds of fva'cid per "100 pounds of volatile free clay at 21.5% concentrationffor 6 hours at from 200 to 210- F. `This claywas Washed'to 22 mg. of KOI-I acidity. 'It-` wasfdried, ground, separated, and pelleted 'according to the above method. Thepellethad l adensity of .852 and the following analysis:

:vPerCellt -`r rsi'oz 77 R203 17.4 YFelo 11.0 "cao -az Mgo 3.6.

When used in theY above method of .catalytic --cr-acking it gave 'thefollowing results:- 410 end- .hpoint gasoline, 25.1%; gas,l3.7%;-. coke,3.4%.`

Example 4 The Cheto clay previously described Was treated with a total of 70 pounds 'of anhydrous sulfuric acid per 100 pounds of volatile free clay, the acid being at 10% concentration for a period of 6 hours at 200 to 210 F., the acid being` added incrementally to maintain a 10%. concentration .throughout the treat. The clay was washed to an acidity of 140 mg. of KOH per .gram by dilut- "ing the materialwithdrawn. from' 3 with `equal parts of Water and ltering. The clay was. dried, ground, and separated. The material withdrawn was then mixed with water containing Y. `enough NI-IlOI-Into forma slurry at5vpH. The `material was then ltered. .The illtencake was washed and .driedand pelleted. sThe pelletshad .28 .af..density of `.596. vThe clay whenemplpyed. in the above cracking method gave the. following re- .sultsz 410 end-point gasoline, 40.6%;,gas,".5 .4%;

carbon. .4.1 Y

Eample Purvis `clay was treated with 50 pounds of'anhydrous sulfuric acidper 100 poundsofl volatile `free clay of 21.5% concentration for 6 hourstat a temperature of 200 to 210 F. The .clay 'was washed, ltered, dried, ground, and separatedfto produce a clay of 22% V. M. 'It Was'pell'ete'd'fin accordance with the methodl previously described. The clay had a residual acidity of 10.6 mg.fof KOI-I per gram of clay. A waterslurry of this clay had a pH of 2.95. The pellets had an apparent density of .8, and when employed in the previouslyideszcribed method of catalysis it gave thefollowing results: 410. end-point gasolina-292%; gas, 3.2%; carbon,'3'.7%.

Example 7 Theclay of Example 6 was treatedin .the .same manner as in Example 6V except thatfammonia vwas-introduced. through linefa suicient....to

bring .the slurry'passinglr to the lter 21to 5 pH.

The dried clay had an acidityof 5.4 5mg.. oiKQI-I per vgram (at V. M. ofy 23.8%). A slurry. of the lclay had apI-I of 4.12. .The clay was pelletedin .the

`same manner as Example 6. The pellets -.hadzan `.appaufent density of .704, and when employed in .the above process of cracking gave .the following results: 410 end-point gasoline, 32.3%; gas, 3.7%; carbon, 2.6%.

`It willfbe observed that the treatment .with-.am-

Hfmonia reduced. theacidity of the clay and gave pellets of decreased apparent density. and yimproved catalytic efficiency. The yield-of kgasoline .obtained was increased. and with reduced carbon formation.

While wehave described a particular embodi- -ment of our. .invention for t-he ,purpose .of .il-

lustration, it .should be understood that. various -f modifications and adaptations thereof may.,be

made within the yspirit of the invention as .set forth in the appended claims.

This application is a division of our co-pendlng application, Serial No. 521,44,.1iled February 7, 1944, which issued as United States LettersPatent-No. 2,432,746, on December 16, .1947.

We claim:

1. A process for the production of an acid4 activated. montmorillonite clay catalyst, which comprises acid treating an acid activatable montmorillonite clay-having base exchangeableions vwith a mineral a-cid'to reduce substantiallythe alumina content of said clay andv increase .its catalytic activity, separating acid from the yclay to produce a clay containing residual .titratable acidity,..and reacting said clay with. ammonium hydroxidein amount suiiicient to introduce ammonium ions into base exchange position on said i clay 'and'to reduce said titratable acidity.

` 2. A process as dened in claim 1 in which the R203 content of the clay, resulting from said acid treating'fliesy Within `the range vof about 10 to 20%, and said residual titratafblel acidityilie's within the range of about 5 to `25 milligrams of :-KOH perv gram.

alytic activity, separating the acid from the clay to produce a clay containing a residual titratable acidity Within the range of from to 140 imilligrams of KOH per gram, and reacting said clay with ammonium hydroxide Ein amount sufficient to introduce from 5 to 80 milliequivalents of ammonium ions into base exchange position on said clay and to reduce the titratable acidity.

4. In the process of producing an acid activated montmorillonite clay `catalyst in which acid activatable montmorillonite clay is activated to catalytic cracking activity by treatment With acid and Washed to remove resulting soluble salts and unreacted acid, the improvement for enhancing the catalytic properties of the acid activated montmorillonite clay catalyst which comprises base exchanging ammonium ions into base exchange positions of said montmorillonite clay and neutralizing acidity of said clay by treating with ammonium hydroxide to a pH Within the range of about 4 to 9.

5. In the process of producing an acid activated montmorillonite clay catalyst in Which acid activatable montmorillonite clay is activated to catalytic cracking activity by treatment with acid and Washed to remove resulting soluble salts and unreacted acid, the resulting montmorillonite clay having an R203 content Within the range of about to 20%, a, base exchange capacity of about 40y to 110 milliequivalents and an acidity of from about 5 to 25 milligrams of KOI-I per gram, the improvement for enhancing the catalytic properties of the acid activated montmorillonite clay catalyst which comprises base exchanging ammonium ions into base exchange positions of said montmorillonite clay so that ammonium ions occupy from about 5 to 80 of said 40 to 110 milliequivalents and neutralizing acidity of said clay by treatment the ammonium hydroxide to a pH within the range of about 4 to 9.

6. An ammoniated acid activated montmorillonite catalyst having ammonium ions in the base exchange positions of said montmorillonite.

'1. An ammoniated acid activated montmorillonite catalyst having ammonium ions in the base exchange positions of said montmorillonite having a pH of 4 to 9.

8. An ammoniated acid activated montmorillonite catalyst having a base exchange capacity of 40 to 110 milliequivalents of which from 5 to 80 .milliequivalents are ammonium ion and the rest comprising calcium and magnesium ions.

9. The process as defined in claim 1 in which ammonia is removed from said clay by heat treatment at 500 F. to 1200" F.

10. The process as defined in claim 3 in which ammonia is removed from said clay by heat treatf' ment at 500 F. to 1200 F.

11. The process as dened in claim 4 in which ammonia is removed from said clay by heat treatnient at 500 F. to 1200 F.

12. The process as defined 1in claim 5 in which ammonia is removed from said clay by heat treatment at 500 F. to 1200o F.

13. An acid activated montmorillonite catalyst produced by heating and thereby removing ammonia from such a catalyst having ammonium ions in the base exchange positions of said montmorillonite.

14. A catalyst as defined in claim 13 yin which the pH of said catalyst before removal of ammonia and having ammonium ions in the base exchange position lies Within the range of about 4 to 9.

15. An acid activated montmorillonite catalyst produced by heating and thereby removing ammonia from such a catalyst having a base exchange capacity of 40- to 110 milliequivalents of which from 5 to 80 milliequivalents are ammonium ion and the rest ycomprising calcium and magnesium ions.

WRIGHT W. GARY. ROBERT B. SECOR. 

